This invention relates to the synthesis of tetrakis (pentafluorophenyl) borates by reaction of a tetrafluoroborate salt with a pentafluorophenyl compound.
It is known to produce tetrakis (pentafluorophenyl) borates by reaction of boron trihalide with pentafluorophenyl lithium or pentafluorophenyl magnesium halide and by reaction of tris (pentafluorophenyl) boron with pentafluorophenyl lithium. See generally, published European patent application No. 0 604 961 A2 and U.S. Pat. No. 5,473,036. Such borates are important intermediates in the synthesis of catalysts used in combination with metallocene polymerization catalysts.
The invention provides a method for the production of tetrakis (pentafluorophenyl) borates by reacting a tetrafluoroborate salt with pentafluorophenyl magnesium halide in a non-interfering solvent.
Pentafluorophenyl magnesium halides (Grignards) are known. See, e.g., Respess, et al., J. Organometal. Chem. (1969) 18:263-274 and Respess, et al., J. Organometal. Chem. (1969) 19:191-195. Pentafluorophenyl magnesium halides useful in the invention have the formula C6F6MgX in which X is a halogen, e.g., iodine, chlorine or bromine, preferably bromine.
Tetrafluoroborate salts useful in the invention have the formula QBF4 in which Q is sodium, lithium or potassium, preferably sodium.
The reaction between the Grignard and the tetrafluoroborate salt may be conducted in any non-interfering solvent. Typical solvents have the formula Rxe2x80x94Oxe2x80x94Rxe2x80x2 in which the R and Rxe2x80x2 are the same or different aliphatic hydrocarbon groups having 2-10 carbon atoms. Ethyl ether is preferred. The reaction is appropriately conducted at a temperature of 0xc2x0 C. to 100xc2x0 C., preferably at 30xc2x0 C. to 35xc2x0 C.
The tetrafluoroborate salt is added to the Grignard solution in stoichiometric amounts or in such greater or lesser amount as may be deemed appropriate. In the preferred practice of the invention the tetrafluoroborate salt is added in an amount more than 15% of stoichiometric.  Preferably the reaction mixture is refluxed to expedite the reaction.